The phrase "a vigorous ally" is correct and usable in written English.
It can be used to describe someone or something that is a strong and active supporter or partner in a particular context, such as politics, business, or personal relationships.
Example: "In the fight against climate change, we need a vigorous ally who can help us implement effective policies."
Alternatives: "a strong supporter" or "an active partner".
But the 70-year-old Mr Aoun, who poses as an arch enemy of Syria and a vigorous reformer, allied himself with pro-Syrian parties.
"We had hoped there would be greater sensitivity to the situation the Philippines finds itself in as one of the most vocal, vigorous allies in the war against terrorism".
Although artists and critics are hardly natural allies, a vigorous public discourse about theater — and that necessarily means an assessment of its quality — is vital to the health of the art form that supports them both.
The United States and its Arab allies mounted a vigorous campaign to isolate Syria, which they accused of sowing chaos and violence throughout the region through its support for militant groups like Hezbollah and Hamas.
Mr. Chagnon and his allies have mounted a vigorous counterattack since the book's contents were described in a widely circulated e-mail written by anthropologists Leslie Sponsel and Terry Turner.
Asked about the remark at a later news conference, Mr. Christopher dismissed Mr. Baker's comments as a "self-serving myth," bluntly adding, "Let me assure you that the presidency goes on until Jan . 20in a vigorous way, and none of our allies are in any doubt as to who's in charge of the government until Jan . 20.
A onetime Baptist missionary, Mr. Pickering ran a vigorous campaign with much help from national Republican allies.
The Emperor attempted, without success, to effect a reconciliation with the Pope, and thereafter the Franciscans and their philosopher ally Marsilius continued to carry on a vigorous antipapal propaganda from the imperial court at Munich.
A vigorous if family-dominated democracy and mineral treasure-chest, Mongolia is a strong Western ally, contributing troops to the wars in both Iraq and Afghanistan.
Juan Peron, a member of the junta, built his following with generous social policies, allied himself with labor and was elected President in 1946 in a vigorous anti-United States campaign.
